Structure and method for facilitating safe downstream passage of migrating fish around hydroelectric projects

ABSTRACT

Structure and method for safe downstream passage of juvenile fish of any species around hydroelectric dam projects using a combination of deeply submerged extended turbine intakes and surface-oriented bypass flows near the dam structure. The turbine intakes are extended upstream from the dam face.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Patent Application Ser. No. 60/873,895 filed Dec. 8, 2006.

BACKGROUND

1. Field of the Invention

The present disclosure relates to structure and method for facilitatingsafe downstream passage of migrating fish around run-of-the-riverhydroelectric projects which include turbine structures, by utilizingnatural fish instincts to avoid entrance into the turbines and whichpromote natural fish movement into safe bypass flows around the damproject.

2. Description of the Prior Art

Hydroelectric projects normally involve a large dam structure withmultiple electrical generator turbines which include turbine intakes onthe upstream face of the dam to channel water flow through the turbineusing the “head” or water pressure from the reservoir on the upstreamside of the dam. Many of these hydroelectric dam projects are located onmajor river systems such as the Snake and the Columbia River systems inthe Northwest United States. These streams or rivers are the naturalhabitat and migration routes for fish, such as but not limited tosalmon. The mature fish return to travel upstream to spawn in the riverand tributaries of the river system and juvenile fish from hatcheries ornatural spawning grounds then instinctively travel downstream to returnto ocean habitats. As can well be appreciated, the problem of providingfor safe passage, of not only the upstream swimming salmon butdownstream migrating juvenile fish, is tremendous. Although manydifferent and even bizarre approaches have been taken, the commonapproach is that of “juvenile fish attraction” as concerns thedownstream migration. To date, none of the efforts to provide safepassage of the juvenile fish around these hydroelectric projects havebeen satisfactory. Each season a highly significant number of juvenilefish are entrained into the turbine intakes where there are “capturewater velocities” and these fish are injured or killed by the turbinesor associated hydraulic forces. There is thus a tremendous need for anew approach in terms of method and structures which will allow thejuvenile fish to bypass the turbine systems and to enter safe bypassflows from the upper levels of the reservoir, around the dam, through asafe bypass route(s) to be discharged into the project tailrace. Thepresent disclosure provides turbine intake structures for utilizing thenatural instincts of the downstream migrating juvenile fish such assalmonids (or other fish species) to provide a safe passage of the fishinto a surface bypass flow around the dam. The present concept, insteadof utilizing the conventional “juvenile fish attraction” approach,presents a fish guidance philosophy 180° from conventional thinking,presenting fish with “the lesser of evils”.

SUMMARY

Structure and method for downstream passage of juvenile salmonids andother fish species utilizes a combination of deeply submerged extendedintakes to hydroelectric projects, i.e. intakes extended upstream fromthe dam face, and surface oriented bypass flows near the dam structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing FIGURE illustrates the typical profile for a turbine intakeon a dam installation.

DETAILED DESCRIPTION

It will be understood that the hydroelectric project schematically shownin the drawing is by way of example and not limitation as a typicalsystem and is not meant to represent any particular project. It willalso be understood that the bypass system (not shown) may be any one ofmany known designs and normally provides a smooth surface flow path nearthe upstream dam face which is considered to be “conventional” andusually designed to convey 5% to 15% (more or less) of the maximumturbine flow downstream along with the safe passage of the juvenilefish. The bypass normally provides smooth acceleration of transportvelocities in a downstream direction and the fish are captured by theaccelerating velocities toward the safe bypass route(s). These fish endup safely discharged into the project tailrace. The details of thebypass system, while necessary for safe passage, are not a part of thepresent guidance system for the migrating juvenile fish.

Referring to the drawing, a schematic cross section of the dam structureis illustrated at 1. The typical turbine intake 2 will normally beprovided with a slotted trashrack or the like which is usually cleanedand maintained by a gantry crane (not shown). The reservoir or pool area4 backed up by the dam provides the hydraulic head for the turbines, thenormal pool level being indicated at 6 and an existing reservoir bottomat 7. According to the present system, an extended intake in the natureof a closed conduit 8 extends the turbine intake upstream and willinclude a lower or floor wall 9 extending along or closely adjacent thereservoir bottom and an inclined upper or ceiling wall 10. The ceilingwall 10 extends from the top of the conventional turbine intakedownwardly toward the floor wall 9, forming an intake opening which issubmerged as deeply as possible at the bottom of the reservoir. Thedirection of flow is, of course, as indicated by the arrows in the bodyof the reservoir 4. In the new intake structure, the conventionaltrashrack, shown in dotted lines at 3, would be moved to the newposition shown at 11. It is of course contemplated that a pier structure12 of concrete or the like would-be installed to support the relocatedtrashracks 11 and also a gantry crane 13 provided to operate thetrashrack in a conventional manner.

The extended turbine intake 8 may range in length, in an upstreamdirection, from 20 to 2000 feet from the dam face. The choice ofdistance for the intake extension will be dependent upon what is“significant” to the targeted juvenile fish species, i.e. the distancethe fish would not swim upstream randomly from the face of the dam tothe intake extension distance. This choice would thus depend upon thebehavior of the targeted fish species. The extended turbine intakeopening would be submerged with the tops of the intake openings being asdeep as practical considering hydraulic modeling, structural andhydraulic calculations, entrance and friction losses (head losses) andpractical experience such as maximum water velocity for intaketrashracks. The deepest possible setting for the tops of the turbineintakes or openings would, of course, be the best. The extended intakes8 would be constructed using cast-in-place concrete, pre-cast concretesections, metal, or any other suitable materials. It is contemplatedthat the intake openings 14 would be submerged in the range of 50-100feet below the surface 6 of the reservoir.

It will be understood, of course, that stop gates for the turbineintakes would remain at the existing location or at any other convenientstop gate location. The fish passage concept includes the considerationthat maximum practical width of the turbine intake openings 14 wouldprovide the deepest submergence depth which would be the best forjuvenile fish passage reasons.

The present concept and guidance method presents the juvenile fish withthe “lesser of evils” for fish passage downstream instead of relying on“juvenile fish attraction” according to presently practiced methods. Thefish migrating downstream in groups or schools such as indicated at 16in the reservoir 4, regardless of their vertical position in the watercolumn, will detect a deep, dark flow movement into the turbine intakeopening 14 accompanied by a relatively rapid flow acceleration,turbulence, noise and some vibration of the trashrack structure.Multiple observations of downstream migrating salmonids for example showthat juvenile fish will be “repulsed” by these conditions and willinstinctively gradually swim away. The initial detection of theseadverse conditions by the fish will be at some distance from theintakes, before “capture water velocities” are present. All the fishinstincts will be to swim away and this will be easily possible atjuvenile fish cruising speeds, the “burst speed” not being necessary.The juvenile fish swimming away from the deep, dark intake openings 14will volitionally and incrementally move into water volumes that areslowly moving toward the dam face by maintenance of the aforementioned5% to 15% (more or less) surface-oriented fish passage systems at ornear the dam face. In short periods of time, fish avoiding the deep,dark intakes would be surrounded by water heading toward the dam face.Once within these water volumes the fish will be randomly “milling”about, swimming short distances without a clear destination discernibleor intended. They will stay within water volumes generally moving slowlytoward the dam face and away from the deep turbine intakes 14 upstream.

Bypass flows within 50 feet vertical of water surface, near or at thedam face will maintain passive (i.e. fish milling randomly) juvenilefish movement towards the dam face for all fish avoiding the deepextended intake openings 14. This is so even though the avoidance may berelatively short term. Surface bypass flows of 5% to 15% of maximumturbine flows are initially considered adequate, and this range of flowscan only be refined by multiple tests of juvenile fish passage withfull-scale facilities. Once at or near the face of the dam the fish willprobably refuse any outlet provided (based on past observations), andwill mill about randomly for hours, days or weeks. They will mill aboutacross the entire water width and depth accessible near the dam facewith no apparent pattern(s) to their movements. It is not expected thatthey would randomly swim upstream as far as the upstream turbine intakeopenings 14 because this movement would defy their downstream migrationinstinct. They will mill about near the dam face as currently observedat many hydroelectric projects. Eventually, their instincts to migratedownstream is expected to overcome their reluctance to enter whateverbypass system is offered, and they enter the bypass system. By reason ofinstinct, there would not be any other route for downstream passageexcept the safe route offered near the dam face. The upstream turbineopenings 14 would no longer be perceived. Fish then entering the bypasssystem(s) encounter a smooth acceleration of transport velocities in adownstream direction, and are captured by the accelerating velocitiestoward the safe bypass route(s). These fish end up discharged safelyinto the project tailrace. It will be understood, of course, that thebypass facilities may include modified spill gates, normal spill gates,upward or downward acting weir gates, Obermeyer gates, rubber dams,surface bypass spills, orifice passages, ice and trash sluiceways(modified for fish passage), sluice gates, and/or any surface-oriented(within top 50 feet of water column) downstream fish passage systemsthat have been successfully implemented to date.

Although the present structure, system and method have been described inconsiderable detail with reference to certain embodiments or methodsteps, other embodiments and method steps are possible within thepurview of this disclosure. Therefore, the spirit or scope of thepresent application should not be limited to the description of theembodiments contained herein.

1. In a dam installation for holding a reservoir of water and includingat least one turbine with an opening on the upstream face of the dam, adownstream passage system for migrating fish traveling in an instinctivefish passage area in said reservoir, comprising; an intake conduitextending from said turbine opening in an upstream direction a distanceexceeding random reverse upstream travel of migrating fish said conduitterminating in an extended turbine intake remote from the face of thedam and closely adjacent the reservoir bottom beneath the instinctivefish passage area, and a dam bypass system in the area of the damcreating flow in the reservoir in the area of the dam face to maintainpassive fish movement toward the dam face and into the downstreampassage system.
 2. The downstream passage system of claim 1 wherein;said intake conduit extends upstream an approximate distance of between20 to 2000 feet.
 3. The downstream passage system of claim 2 whereinsaid extended intake is located an approximate distance of between 50 to100 feet below the upper surface of the reservoir.
 4. The downstreampassage system of claim 3 wherein the bypass flow rate is withinapproximately 5%-15% of the maximum turbine flow rate.
 5. The downstreampassage system of claim 4 wherein said bypass system is located withinthe top 50 feet of the reservoir water column.
 6. In a dam installationfor holding a reservoir of water in a flowing stream or river course andincluding a turbine structure with a turbine opening in the upstreamface of the dam for channeling water through the turbine, said reservoirproviding a hydraulic head for driving said turbine, a safe instinctivedownstream passage system providing avoidance of said turbine structureby migrating fish traveling in an instinctive fish passage area locatedin the upper levels of said stream or river, comprising; an intakeconduit extending from said turbine opening in an upstream directionaway from the dam face, said intake conduit having a bottom wall portionlocated closely adjacent the bottom of said reservoir and a top wallportion downwardly inclined from the upper portion of said turbineopening toward the bottom wall portion and configured to form anextended turbine intake remote from the face of the dam and below saidinstinctive fish passage area, said extended intake being located adistance from the upstream dam face that exceeds the observed randomreverse upstream travel of migrating fish of a targeted species and deepenough to avoid intake of migrating fish instinctively sensing andseeking to avoid the capture water velocity, turbulence and vibrationsassociated with the intake, said extended intake being of maximum widthaccording to hydraulic modeling and dimensioned to provide sufficientflow characteristics according to turbine intake requirements, a dambypass system in the upper level of said reservoir in the area of thedam face for guiding fish around the dam and into the project tailrace,said bypass system creating a smooth flow in the reservoir in the areaof the dam face to maintain fish movement toward the dam face and intothe bypass system for all fish avoiding the deep extended turbineintake, said bypass system presenting the only route for continuedinstinctive downstream migration travel.
 7. The downstream passagesystem of claim 6 wherein; said intake conduit extends upstream anapproximate distance of between 20 to 2000 feet.
 8. The downstreampassage system of claim 7 wherein said extended intake is located anapproximate distance of between 50 to 100 feet below the upper surfaceof the reservoir.
 9. The downstream passage system of claim 8 whereinthe bypass flow rate is within approximately 5%-15% of the maximumturbine flow rate.
 10. The downstream passage system of claim 9 whereinsaid bypass system is located within the top 50 feet of the reservoirwater column.
 11. The downstream passage system of claim 10 wherein thetargeted fish are migrating juveniles.
 12. The downstream passage systemof claim 11 wherein the targeted fish species are salnonids.
 13. Thedownstream passage system of claim 10, including; a plurality of saidturbines, intake conduits and extended turbine intakes.
 14. Thedownstream passage system of claim 13 wherein each said extended turbineintakes include a trashrack across the opening thereof, said systemincluding; a pier system for supporting said extended turbine intakes,and a gantry crane system for serving said extended intakes and trashracks.
 15. A method for safe downstream passage of migrating fish arounda dam project including at least one turbine comprising the steps of;extending the turbine intake upstream from the dam a distance exceedingobserved random reverse upstream travel of migrating fish, placing saidturbine intakes below migrating fish travel in the upper level of thedam reservoir to create deep intake turbulence and vibration wherebymigrating fish instinctively avoid captive water velocity flow, creatinga bypass flow to maintain passive fish movement toward the dam face andinto a safe downstream passage system.
 16. A method for providing safedownstream passage of migrating fish around a dam installation forholding a reservoir of water; said installation including at least oneturbine having a turbine intake on the upstream face of the dam and adownstream passage system for migrating fish traveling in an instinctivefish passage area in said reservoir comprising the steps of; extendingsaid turbine intake in an upstream direction a distance exceeding randomreverse upstream travel of migrating fish, locating said turbine intakeadjacent the reservoir bottom beneath the instinctive fish passage area,and creating a bypass flow in the area of the dam to maintain passivefish movement toward the dam face and into the downstream passagesystem.
 17. The method of claim 16 wherein said extended turbine intakeis extended upstream a distance of between 20 to 2000 feet.
 18. Themethod of claim 17 wherein said extended turbine intake is located anapproximate distance of between 50 to 100 feet below the surface of thereservoir.
 19. The method of claim 18 wherein the bypass flow has a flowrate within approximately 5%-15% of the turbine flow rate.
 20. Themethod of claim 19 wherein said bypass flow is created within the top 50feet of the reservoir water column.